Adjustable biasing device for sheet media feeder

ABSTRACT

An adjustable biasing device for a sheet media feeder is disclosed. The adjustable biasing device biases sheets of media toward a media engaging structure and has an adjustment control for modulating the amount of force applied by the biasing device to the sheets of media.

BACKGROUND

Sheet media feeders are widely used in a variety of devices such as in printers, copy machines, facsimile machines and the like. In general, sheets of media, such a paper, and the like, are stored in a stack of media, and the sheet media feeder includes engaging structures, such as a roller or the like, for separating one sheet from the stack and urging it along a media path of the device.

In order to ensure consistent and reliable separation of the sheet of media from the stack of media, the sheet of media typically engages the engaging structure within a predefined range of force between the sheet of media and the engaging structure. If too much force is applied, the sheet may not separate from the stack, and if too little force is applied, the sheet may not properly engage the engaging structures.

In many situations, it is undesirable to apply a large biasing force to a large stack of media. For example, where the individual sheets of media form a vertical stack of media, and those sheets of media are relatively massive and/or fragile, such as when they are individual polymer identification cards or the like being fed through an identification card printer, the weight of the large stack of media tends to urge the lowest sheet of media within that stack toward the engaging structure. Accordingly, it may be unnecessary to apply any additional biasing force to the stack of media, and such additional force creates extra load to the engaging structure and ultimately to the driving mechanism causing system stall.

Similarly, as the sheets of media are consumed from the stack of media, the weight of the stack of media is reduced. Accordingly, the remaining stack of media cannot contribute significantly to the biasing of the bottom most sheet of media toward the engaging structure.

Therefore, the force applied to the stack of media is desirably sufficient to urge the bottom most sheet of media in the stack of media toward the engaging structure when the stack of media is nearly depleted, while still preventing excessive force from being applied when the stack of media is large. In practice, this characteristic tends to limit the size or height of the stack of media allowed within the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a back isometric view of a printer having a sheet media feeder with a stacked media-biasing device therein in accordance with an embodiment of the present invention.

FIG. 2 is an isometric lower view of the sheet media feeder that is installed on a media engaging structure, with a stacked media-biasing device of FIG. 1.

FIG. 3 is a fragmentary top isometric view of the sheet media feeder of FIG. 2 with a portion of the cover removed to show internal detail and a possible full stack of media.

FIG. 4 is the fragmentary top isometric view of the sheet media feeder with a portion of the cover removed of FIG. 3 showing a possible substantially depleted stack of media.

FIG. 5 is an enlarged isometric view of a portion of the biasing structure of the sheet media feeder of FIG. 2.

FIG. 6 is a fragmentary cross-sectional view taken along line 6-6 of FIG. 4.

FIG. 7 is a fragmentary cross-sectional view taken along line 7-7 of FIG. 3.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

A biasing device 20 for a sheet media feeder 22 that allows the amount of force applied to a stack of media 10 to be optimized as the stack of media 10 is depleted is disclosed in FIGS. 1-7.

1. Exemplar Media-Path Bearing Device

Referring to FIG. 1, the sheet media feeder 22 containing the biasing device 20 is operably secured to a media-path bearing device 24, such as a printer 24′, copier, facsimile machine or the like. The media-path bearing device 24 shown in FIG. 1 may bean inkjet printer 24′ or other suitable printer containing the sheet media feeder 22 detachably secured thereto.

In one implementation, the inkjet printer 24′ includes a chassis 30, the sheet media feeder 22 for supplying sheets of media 32 to the printer 24′ via a media path 34, and a movable print carriage for moving one or more printheads relative to the sheet of media 32 at a print zone. The sheets of media 32 may be any type of suitable sheet material, such as paper, card-stock, transparencies, mylar, foils, and the like, but for convenience, the illustrated embodiment is described using a substantially planar, polymer card that includes a planar surface 36 (FIGS. 6 & 7) adapted to be printed thereon. Such cards are often used to produce identification badges, driver's licenses, and the like.

The sheet media feeder 22 moves the sheet of media 32 into the print zone from a storage chamber 38 along the media path 34, using a series of motor-driven rollers or the like, here rollers 40 a, 40 b, which are secured to the printer so as to engage the detachable sheet media feeder, are shown in FIG. 2. A plurality of sheets of media 32 forming a substantially vertical stack of media 10 is stored within the storage chamber 38 thereby defining a stack height 42 (FIG. 7).

In the print zone, the sheets of media 32 receive ink from a printhead, which is operably secured to the carriage (not shown). The carriage is usually driven by a conventional drive belt/pulley and motor arrangement along a guide rod or the like. The guide rod defines a scanning direction or scanning axis along which the printheads traverse over the print zone. The printheads selectively deposit one or more ink droplets on the planar surface of the sheet of media located in the print zone in accordance with instructions from a printer controller, such as a microprocessor, which may be located within chassis 30.

The controller may receive an instruction signal from the microprocessor based on sensors along the media path 34, and from a host device (not shown). The printhead carriage motor and the media delivery system drive motor operate in response to the printer controller, which may operate in a manner well known to those skilled in the art.

In other embodiments, a laser print engine or other suitable print engine may be used instead of an inkjet print engine.

2. Sheet Media Feeder

As shown in FIGS. 2-4, the sheet media feeder 22 may include a frame 44 defining the storage chamber 38 therein for receiving the stack of media 10 so as to allow an outer most sheet of media 32 within the stack of media 10 to engage the media engaging structure 12, such as a roller 40 c or the like. Accordingly, the media engaging structure 12 thereby engages and separates, one-by-one, individual sheets of media 32 from the stack of media 10, and urges each sheet from the stack of media 10 along the media path 34.

The frame 44 can have at least one side 46 and the stack of media 10 rests within the storage chamber 38 adjacent to the at least one side 46. In one implementation, the frame 44 has a lower side 46′ and an upper side 48 and the stack of media 10 is stacked substantially vertically on the lower side 46′ with the media engaging structure 12 positioned adjacent to the lower side 46′ as shown in FIG. 2. The media engaging structure 12 extends through an opening 50 in the lower side 46′ of the frame 44 to operably engage the lowest most sheet of media 32 a within the stack of media 10 and urge the lowest most sheet of media 32 a through a slot 52 in the frame toward additional downstream rollers 40 a, 40 b or the like along the media path 34. The frame 44 can include a base structure 44 a with a transparent cover 44 b detachably secured thereto thereby allowing the stack of media 10 to be viewed through the cover 44 b.

The biasing device 20 operably engages the stack of media 10 to bias the stack of media 10 towards the media engaging structure 12. In the illustrated example embodiment, the biasing device 20 applies a force substantially normal to a planar surface 54 on the stack of media 10, and the amount of force applied by the biasing device 20 to the stack of media 10 is adjustable so that the amount of force applied may be optimized as the stack of media 10 is depleted from the storage chamber 38.

For example and as shown in FIGS. 3-7, a compression spring 56 can extend between the frame 44 and the stack of media 10, with a threaded adjustment control 60 operably secured to a first end 62 of the compression spring 56 as shown. The threaded adjustment control 60 is operably received is within a mating threaded opening 64 on the frame 44 so as to allow the adjustment control 60 to move toward the stack of media 10 by turning the adjustment control 60 within the threaded opening 64. Accordingly, by turning the treaded adjustment control 60 in a first direction 68 (FIG. 3), the adjustment control 60 moves closer to the stack of media 10, thereby driving out more pitches of the spring 56 against the stack of media 10 and increasing the amount of force applied to the stack of media 10.

In order to prevent the second end 70 of the compression spring 56 from adversely impacting the upper most sheet of media 32 b of the stack of media 10, a spring engaging structure 72 can be positioned between the stack of media 10 and the second end 70 of the compression spring 56. In one possible implementation, the spring engaging structure 72 has a substantially planar member 74 that engages the upper most sheet of media 32 b of the stack of media 10 on a first side 76, and has a protrusion 78 extending from its opposite second side 80 toward the threaded opening 64. A disk 82 that is sized to engage the second end 70 of the compression spring 56 is rotatably secured to the protrusion 78. Accordingly, when the adjustment control 60 is rotated within the threaded opening 64, the compression spring 56 will necessarily rotate and cause the second end 70 to spin the disk 82 about the protrusion 78 and thereby prevent the second end 70 from digging into the stack of media 10 or otherwise hindering rotation of the compression spring 56 and adjustment control 60. The disk 82 can also include a strain gauge 84 or the like thereon which is visible through the frame 44 thereby allowing the amount of force applied by the compression spring 56 to the stack of media 10 to be monitored and tuned accordingly.

The treaded adjustment control 60 can include a knob portion 90 that allows a user to easily grasp and rotate the adjustment control 60. In one possible implementation, the knob portion 90 includes a position indicator 92 such as an elongate needle portion or the like to provide a user with a visual indication of the position of the knob portion 90 relative to the frame 44.

The threaded opening 64 can be a threaded and tapered collar 64 a received within the upper side 48 of the frame 44. The collar 64 a can have a threaded length 94 that provides the adjustment control 60 sufficient range of movement therein so as to allow the compression spring 56 to provide an optimal force between the stack of media 10 and the engaging structure 12, even when the stack of media 10 is substantially depleted or even if only one sheet of media 32 is remaining from the stack of media 10.

As shown in FIGS. 6 & 7, the compression spring 56 can also be retractable within the threads of the threaded opening 64, thereby defining a retracted position 100 as shown in FIG. 7 and an extended position 102 as shown in FIG. 6. In one possible implementation, the pitch 104 of the threaded opening 64 is less than the pitch 106 (FIG. 5) of an unloaded portion of the compression spring 56. Accordingly, the retained portion 108 of the compression spring 56 received within the threaded opening 64 is compressed to optimize space, while not allowing the retained portion 108 of the compression spring 56 to contribute to the force applied to that stack of media 10. Since, only the extended portion 110 of the compression spring 56, that is the portion that extends between the threaded opening 64 and the stack of media 10 applies a force to the stack of media 10, the amount of force applied to a full stack of media 10′ (FIG. 7) can be minimized, while still allowing the force applied to a substantially depleted stack of media 10″ (FIG. 6) to be increased as needed for proper engagement between the sheet of media 32 a and the engaging structure 12.

The difference in pitch 104 (FIG. 6), 106 (FIG. 5) between the threaded opening 64 and the uncompressed spring 56 also serves to limit the direction of rotation of the adjustment control 60. The adjustment control 60 can be easily rotated in the first direction 68 within the threaded opening 64 so as to uncoil the spring 56 from the threaded opening 64 and thereby increase the amount of force applied by the compression spring 56. However, an extended compression spring 56 will not as easily be compressed back into the threaded opening 64 by turning the adjustment control 60 in the opposite second direction, thereby limiting a user's ability to inadvertently reduce the amount of force applied by the spring 56 as the stack of media 10 is depleted.

The adjustability of the biasing device 20 allows a full stack of media 10′ (FIGS. 3 & 7) to be stored within the storage chamber 38 without compromising the biasing force applied to a substantially depleted stack of media 10″ (FIGS. 4 & 6) and without applying too much force when the stack of media 10 is substantially full. Accordingly, an operator need not replenish or replace the stack of media 10 as frequently for engaging reliability reasons.

Moreover, the rectractability of the spring 56 within the threaded opening 64 also allows the biasing force applied to the stack of media 10 to be minimized when not needed, such as during storage and/or shipment of the media feeder 22 containing the stack of media 10. Common biasing structures usually store and ship the media feeder containing the stack of media with the compression spring fully compressed against the stack of media, thereby applying the maximum biasing force to the stack of media for extended periods of time. Accordingly, such forces can tend to damage the sheets of media within the stack, particularly, where the media are sheets of resilient, polymer cards used for identification badges and the like.

3. Use and Operation

A user activates the adjustable biasing device 20 by turning the adjustment control 60 as needed to apply the necessary force to the stack of media 10. The position indicator 92 and, if installed, the transparent cover 44 b and strain gauge 84 allow the user to see if the second end 70 of the spring is operably engaging the stack of media 10 and adjust the biasing force applied as needed. Moreover if desired, the frame 44 includes surface ornamentation thereon relative to defined aligned positions of the position indicator 92 thereby allowing a user to position the knob portion 90 of the adjustment control 60 for a known stack size or the like.

In an example embodiment, the sheet media feeder 22 is a pre-packaged cartridge-style structure that contains a full stack of media therein. The structure can arrive with the biasing device 20 in its retracted position 100 so as to prevent excessive force from being applied to the stack of media 10 during initial transport and storage of the structure. A user obtains a new sheet media feeder 22 and turns the adjustment control 60 to a defined position so as to extend the spring 56 from the threaded opening 64 and apply a biasing force to the stack of media 10. The user then installs the sheet media feeder 22 on the media-path bearing device 24, such as a printer 24′ or the like.

As the printer 24′ is used and the sheets of media 32 are depleted one-by-one, from the stack of media 10, the user turns the adjustment control 60, so as to maintain a desirable biasing force on the stack of media 10. If available, the user can align the position indicator 92 on the adjustment control 60 to defined positions for the detected stack height 42 of the stack of media 10. This process of adjusting the adjustment control 60 is repeated as needed during depletion of sheets of media 32 from the stack of media 10 thereby maintaining optimal biasing force on the stack of media 10 as it is being depleted.

Alternatively, in cases where the strain gauge 84 is installed, the user can position the adjustment control 60 so as to maintain the force applied to the strain gauge 84 within a predetermined range. As the detected force drops below a predefined limit, the user readjusts the position control 60 accordingly so as to return the force applied to the strain gauge 84 to within the predetermined range.

Also, in cases where a transparent cover 44 b is installed, the user can view through the transparent cover 44 b the engagement between the second end 70 of the biasing device 20 and the substantially planar member 74. Should the second end 70 ever become disengaged from the substantially planar member, the user can position the adjustment control 60 so as to move the second end 70 toward the substantially planar member 74, thereby increasing the biasing force applied to the stack of media.

In view of the wide variety of embodiments to which the principles of the invention can be applied, it should be apparent that the detailed descriptions of exemplar embodiments are illustrative only and should not be taken as limiting the scope of the invention. For example, exemplar type of media-path bearing device is for illustrative purposes only. Accordingly, the claimed invention includes all such modifications as may come within the scope of the following claims and equivalents thereto. 

1. A sheet media feeder, comprising: a biasing structure to bias media sheets toward a media engaging structure; and, an adjustment control operably secured to the biasing structure to adjust a biasing force applied to the media sheets, wherein said biasing structure is operably received within an opening.
 2. The adjustable biasing device of claim 1, wherein said biasing structure is a spring.
 3. The adjustable biasing device of claim 2, wherein said spring is a compression spring.
 4. The adjustable biasing device of claim 2, wherein said spring is retractable within said opening defining a retracted position.
 5. The adjustable biasing device of claim 4, wherein said adjustment control extends a portion of said spring from said opening.
 6. The adjustable biasing device of claim 5, wherein: said sheet media feeder has a frame; said opening is defined by a threaded collar operably secured to said frame; and, said adjustment control is a threaded member sized to engage said threaded collar defining a first direction of rotation of said threaded member relative to said threaded collar in which said spring is moved toward said stack to increase the force applied by the spring to said stack.
 7. The adjustable biasing device of claim 6, wherein said threaded member resists movement in an opposite second direction of rotation.
 8. The adjustable biasing device of claim 4, wherein: said opening is threaded with a first defined pitch; said spring is a coil spring having a second defined pitch; and, said spring is operably received within the threads of said opening in said retracted position.
 9. The adjustable biasing device of claim 8, wherein said first defined pitch is less than said second defined pitch.
 10. The adjustable biasing device of claim 4, wherein said opening is a threaded opening, and said adjustment control is a threaded control knob operably secured to said threaded opening.
 11. The adjustable biasing device of claim 10, wherein said threaded control knob has a visual position indicator operably secured thereto.
 12. The adjustable biasing device of claim 10, further including a strain gauge operably secured to the biasing member.
 13. A printer comprising: a biasing device adapted to apply a biasing force urging a stack of media toward a media engaging structure; and, an adjustment control operably secured to said biasing device for adjusting the amount of biasing force urging the stack of media toward the media engaging structure, wherein said biasing device is operably received within an opening.
 14. The printer of claim 13, further including a media storage device secured to a chassis.
 15. The printer of claim 14, wherein said media storage device is detachably secured to the chassis.
 16. The printer of claim 13, wherein said printer is an ink jet printer.
 17. The printer of claim 13, wherein said sheets of media are substantially planar cards.
 18. The printer of claim 13, wherein: said biasing device is a spring operably engaging said stack of media; said spring is retractably received within said opening to define a retracted portion received within said opening and an extended portion extending from said opening toward said stack of media; said retracted portion having a defined length; and, said adjustment control regulates the defined length of said retracted portion.
 19. The printer of claim 18, wherein: said biasing device is a compression spring having a first end and an opposite second end, said second end operably engaging said stack of media; said compression spring retractably received within a opening at said first end; and, said adjustment control regulates the amount of the compression spring received within the opening.
 20. The printer of claim 19, wherein said second end is detachable from said stack of media, and said spring is fully retractable within said opening.
 21. A media feeder for a media path bearing device, the media-path bearing device having a media engaging structure for engaging media within the media feeder and urging the media along the media path, the media feeder comprising; a frame operably secured to the media-path bearing device, the frame having a storage chamber for storing a plurality of sheets of media in a stack thereby defining a stack of media, said stack of media positioned adjacent to the media engaging structure so as to allow individual sheets of media from said stack of media to be removed one-by-one by the media engaging structure; a biasing device operably secured to the frame and extending between the frame and the stack of media so as to apply a biasing force urging the stack of media toward the media engaging structure; and, an adjustment control operably secured to said biasing device for adjusting the amount of biasing force urging the stack of media toward the media engaging structures wherein said biasing device is operably received within an opening.
 22. The media feeder of claim 21, wherein said frame is detachably secured to the media-path bearing device.
 23. A media feeder for a media path bearing device, the media-path bearing device having a media engaging structure for engaging media within the media feeder and urging the media along the media path the media feeder comprising: a frame operably secured to the media-path bearing device, the frame having a storage chamber for storing a plurality of sheets of media in a stack thereby defining a stack of media, said stack of media positioned adjacent to the media engaging structure so as to allow individual sheets of media from said stack of media to be removed one-by-one by the media engaging structure, a biasing device operably secured to the frame and extending between the frame and the stack of media so as to apply a biasing force urging the stack of media toward the media engaging structure; and an adjustment control operably secured to said biasing device for adjusting the amount of biasing force urging the stack of media toward the media engaging structure, wherein: said frame comprises a substantially planar base structure and a cover operably secured thereto to define the media chamber therein; and, said cover is transparent to allow viewing of said biasing device therethrough.
 24. A media feeder for a media path bearing device, the media-path bearing device having a media engaging structure for engaging media within the media feeder and urging the media along the media path. the media feeder comprising: a frame operably secured to the media-path bearing device, the frame having a storage chamber for storing a plurality of sheets of media in a stack thereby defining a stack of media, said stack of media positioned adjacent to the media engaging structure so as to allow individual sheets of media from said stack of media to be removed one-by-one by the media engaging structure; a biasing device operably secured to the frame and extending between the frame and the stack of media so as to apply a biasing force urging the stack of media toward the media engaging structure; and an adjustment control operably secured to said biasing device for adjusting the amount of biasing force urging the stack of media toward the media engaging structure, wherein: said biasing device is a spring operably engaging said stack of media; said spring retractably received within a opening to define a retracted portion received within said opening and an extended portion extending from said opening toward said stack of media; said retracted portion having a defined length; and, said adjustment control regulates the defined length of said retracted portion.
 25. The media feeder of claim 24, wherein: said opening is threaded defining threads therein having a defined first pitch; said spring is a coil spring defining coils having a defined second pitch in an uncompressed position; and, said coils forming the retracted portion are received within the threads of said opening.
 26. The media feeder of claim 25, wherein said defined first pitch is less than said defined second pitch.
 27. A method for biasing sheets of media forming a stack of media within a media feeder said method comprising: applying a biasing force substantially normal to the stack of media; removing sheets of media from the stack of media; and, adjusting the magnitude of the biasing force applied by the media biasing device to the stack of media wherein said media biasing device is operably received within an opening.
 28. The method for biasing sheets of media of claim 27, further comprising: storing the media feeder containing the stack of media therein without the media biasing device applying a substantial biasing force to the stack of media; and, operably connecting the media biasing device to the stack of media prior to using the media feeder.
 29. The method for biasing sheets of media of claim 27, wherein said biasing device is a compression spring having a first end received within an opening in the media feeder and an opposite second end operably engaging said stack of media; and said adjusting the amount of biasing force step includes comprises: extending a portion of said compression spring from said opening as said stack of media is depleted.
 30. The method for biasing sheets of media of claim 27, further comprising detecting the amount of force applied by the biasing device to the stack of media.
 31. The method for biasing sheets of media of claim 27, wherein said adjusting the amount of biasing force further comprises positioning a control knob at a predetermined position relative to a detected size of said stack of media.
 32. A sheet media feeder comprising: means for biasing media sheets toward means for engaging media; and, means for adjusting a biasing force applied to the media sheets by the means for biasing, wherein said means for biasing is operably received within an opening.
 33. The sheet media feeder of claim 32, wherein said means for biasing is a spring.
 34. The sheet media feeder of claim 32, wherein said means for adjusting is a threaded control knob operably secured to the means for biasing and operably received within a threaded opening on the sheet media feeder.
 35. The sheet media feeder of claim 34, wherein said threaded opening defines a threaded collar.
 36. The media feeder of claim 23, wherein said frame is detachably secured to the media-path bearing device.
 37. The media feeder of claim 23, wherein: said biasing device is a spring operably engaging said stack of media; said spring retractably received within a opening to define a retracted portion received within said opening and an extended portion extending from said opening toward said stack of media; said retracted portion having a defined length; and said adjustment control regulates the defined length of said retracted portion.
 38. A method for biasing sheets of media forming a stack of media within a media feeder said method comprising: applying a biasing force substantially normal to the stack of media; removing sheets of media from the stack of media; adjusting the magnitude of the biasing force applied by the media biasing device to the stack of media; storing the media feeder containing the stack of media therein without the media biasing device applying a substantial biasing force to the stack of media; and operably connecting the media biasing device to the stack of media prior to using the media feeder.
 39. The method for biasing sheets of media of claim 38, wherein said biasing device is a compression spring having a first end received within an opening in the media feeder and an opposite second end operably engaging said stack of media; and said adjusting the amount of biasing force comprises: extending a portion of said compression spring from said opening as said stack of media is depleted.
 40. The method for biasing sheets of media of claim 38, further comprising detecting the amount of force applied by the biasing device to the stack of media.
 41. The method for biasing sheets of media of claim 38, wherein said adjusting the amount of biasing force further comprises positioning a control knob at a predetermined position relative to a detected size of said stack of media.
 42. A method for biasing sheets of media forming a stack of media within a media feeder said method comprising: applying a biasing force substantially normal to the stack of media; removing sheets of media from the stack of media; and adjusting the magnitude of the biasing force applied by the media biasing device to the stack of media, wherein said biasing device is a compression spring having a first end received within an opening in the media feeder and an opposite second end operably engaging said stack of media; and said adjusting the amount of biasing force comprises: extending a portion of said compression spring from said opening as said stack of media is depleted.
 43. The method for biasing sheets of media of claim 42, further comprising: storing the media feeder containing the stack of media therein without the media biasing device applying a substantial biasing force to the stack of media; and operably connecting the media biasing device to the stack of media prior to using the media feeder.
 44. The method for biasing sheets of media of claim 42, further comprising detecting the amount of force applied by the biasing device to the stack of media.
 45. The method for biasing sheets of media of claim 42, wherein said adjusting the amount of biasing force further comprises positioning a control knob at a predetermined position relative to a detected size of said stack of media.
 46. A method for biasing sheets of media forming a stack of media within a media feeder said method comprising: applying a biasing force substantially normal to the stack of media; removing sheets of media from the stack of media; adjusting the magnitude of the biasing force applied by the media biasing device to the stack of media; and detecting the amount of force applied by the biasing device to the stack of media.
 47. The method for biasing sheets of media of claim 46, further comprising: storing the media feeder containing the stack of media therein without the media biasing device applying a substantial biasing force to the stack of media; and operably connecting the media biasing device to the stack of media prior to using the media feeder.
 48. The method for biasing sheets of media of claim 46, wherein said biasing device is a compression spring having a first end received within an opening in the media feeder and an opposite second end operably engaging said stack of media; and said adjusting the amount of biasing force comprises: extending a portion of said compression spring from said opening as said stack of media is depleted.
 49. The method for biasing sheets of media of claim 46, wherein said adjusting the amount of biasing force further comprises positioning a control knob at a predetermined position relative to a detected size of said stack of media.
 50. A sheet media feeder comprising: means for biasing media sheets toward means for engaging media; and means for adjusting a biasing force applied to the media sheets by the means for biasing, wherein said means for adjusting is a threaded control knob operably secured to the means for biasing and operably received within a threaded opening on the sheet media feeder.
 51. The sheet media feeder of claim 50, wherein said threaded opening defines a threaded collar.
 52. The sheet media feeder of claim 50, wherein said means for biasing is a spring. 